(1) Field of the Invention
This invention relates to an apparatus for producing the wooden heads of golf clubs. More particularly, the invention relates to a compression molding apparatus for producing the wooden heads which are precise in their dimensions and durable in use.
(2) Description of Prior Art
There are two kinds of golf clubs, that is, wood clubs and iron clubs. Further, it is well known that the wooden heads of wood clubs are produced by employing compression molding method.
As is now done in the manufacture of compressed baseball bats, the compression molding process is employed in order to extend the shooting range. During the process of compression molding of wooden heads, their whole bodies are made somewhat larger than the designed dimensions, the wooden heads are then impregnated with a thermosetting or thermoplastic resin liquid, such as phenol resin or urethane resin, and the resin-impregnated heads are subjected to heat and pressure by compression molding so as to cure the impregnated resin and to compress the wooden heads to the designed dimensions.
In this compression molding, an upper and a lower mold half are generally employed in the conventional method. When only two mold members are used in the compression molding, pressure is applied only in the vertical directions, so that it becomes difficult to eliminate the dimensional errors of wooden head materials and to apply even compression effect to all surfaces of the wooden head materials. In other words, with such upper and lower mold members, the wooden head materials are squeezed vertically and the force to deform radially or horizontally acts on them.
In another conventional method, for example, wooden head materials are impregnated with vinyl monomer and the impregnated resin is cured by applying heat or radiant rays without the application of compression. In such method, the resin-impregnated wooden head materials are swollen and the products are neither dense nor tough. Accordingly, it becomes impossible to hit golf balls to a distance with good hitting sounds.
Furthermore, the wooden head materials are not evacuated before they are supplied with resin liquid in the conventional art so that the wooden head materials cannot be fully impregnated with the resin liquid to their innermost portions even when pressure is applied in the impregnation process, because the air remaining in woody tissue of wooden head materials obstructs the impregnation. The products made from such wooden head materials are liable to suffer from cracking, or deformation owing to absorption of moisture or external impact.